The Impact of Reduced Injected Radioactivity on Image Quality of Molecular Breast Imaging Tomosynthesis

This study's objective is to compare image quality in 3-D molecular breast imaging tomosynthesis (MBIT) with that in planar molecular breast imaging (MBI) over a range of breast radioactivity concentrations. Using gelatin and point source phantoms lesion contrast, lesion signal-to-noise ratio (SNR) and spatial resolution were compared for a range of lesion sizes and depths. For both MBI and MBIT, lesion contrast is essentially constant with changing activity while SNR decreases by a factor of 1.5 - 2 between 100% and 25% activity levels. For nearly all lesion sizes and locations contrast and SNR are significantly higher for MBIT than MBI, potentially permitting greater reductions in injected dose. Spatial resolution in MBI is dependent on lesion depth but independent of lesion location with MBIT. Reconstructed MBIT spatial resolution is substantially better than that in the projection images, suggesting future use of higher sensitivity collimators for even further reductions in injected activity.